Control track sound reproducer



Jan. 12, 1943. H. l. RElsKlNu 'Y 2,308,456

CONTROL TRACK SIOUND RBPRQDUCER Filed March 30, 1940 Huf/e fi Ffm t) FM 75e i l l HMH l Bnnentor Gttorncg Patented Jan. 12, 1943 YUNITI-:n 4STATES PATENT vorrlcia:

CONTROL TRACK SOUND BEPRODUCER Hillel 1. misma, Camden, N. J., assigner to nadio Corporation of America, a corporation of Delaware Application March 30, 1940, ,SeriallNo. 326,912v 14 Claims. (Cl. 179-1003) This invention relates to control tracksound reproducers of the same general type as described and claimed, for example, in Weinberger Patent No. 1,850,701, but 'pertains particularly to a method of and apparatus for rendering the operation of the control track independent of any a reading of the followingspecication and ariV inspection of the accompanying drawing, in

which variations in exciter lamp brightness, photocell.

sensitivity, average lm density, or the like.

In the said' Weinberger patent there is disclosed apparatus for reproducing sound from a sound record and for simultaneously controlling the location or volume of the reproduction, .or both, by means of a separate record. One diiiculty which has been encountered in the operation of such apparatus is that any lVariation in the brightness of the exciter lamp? which is used in reproduction of the control record or any Varia.- tion in the average density of the control' record may cause a corresponding variation in the effect of the control record on the sound reproduction.

-In the apparatus of the present invention, these I undesirable effects are avoided by providing an additional control record of constant frequency and amplitude when making the original recording. When the records are `reproduced,this constant frequency, constant amplitude record is used to control a variable gain amplifier so that this record is reproduced at a constant amplitude irrespective of variations of the exciter lamp brightness, photocell `sensitivity or lm density, and this same amplifier is used in the reproduction of the other control records, thereby rendering the effect of all of the control records free from variations.

One object of the invention is to provide an improved apparatus for reproducing control tracks.

Another object of the invention is to provide an improved apparatus for simultaneously reproducing a plurality of control tracks at an ampli-- tude independent of variations in the brightness of the reproducing light source.

Another object of the invention is to provide an apparatus for reproducing a plurality of control tracks wherein' one of the control. tracks controls the amplitude of reproduction of the other control tracks.

Another object of the inventionis to provide an improved sound -reproducer in which the volume of reproduced sound is independent of variations of the brightness of the exciter lamp sensitivity of the photocell or of the density of the sound record.

Other and incidental objectsl of the invention will be apparent to those skilled 'in the'art from Figure 1 is a schematic illustration of the re- A cording apparatus, and

Figure 2 is a schematic illustration of the reproducing apparatus. i l

IAlthough the apparatus is hereinafter described as a sound recording and reproducing ap-v paratus, it should be understood thatthe sound recorders and reproducers are not shown, the drawing showing only the mechanism for recording and reproducing the control tracks which are used in controlling the sound records themselves in the same manner as described in the aforesaid Weinberger patent or as described in Burrill application Serial No. 181,634, led December 24, 193-7 (RCV Docket 5098) orBllnill appli' cation Serial No. 181,635,led December 24, 1937 (RCV Docket 5100) Referring rst to Fig. 1, .a plurality of oscillaters I0, II, I2 and I3 are shown for producing the control frequencies. Each of these oscillators is shown as provided with an appropriate volume control potentiometer such as I4, I5, I6 and I'I, and the output from these potentiometers is fed through ampliler I8 to the recorder I9, where the several control frequencies are recorded on an appropriate medium, such as nlm or disc, as the case may be.

The several control frequencies are preferably so chosen that they may be easily separated by electrical lters. For this purpose, the frequencies should be separated ,by appropriate bands, and they preferably shold not be multiples ofv each other so as to avoida circuit intended to separate a higher frequency from also picking up harmonics of a lower frequency.-

For purposes of illustration, we may assumethat such frequencies as 450 cycles, 1100 cycles, 1400 cycles, and 1900 cycles are chosen as the 'respecticey control frequencies supplied by the oscil application Serial No. 33,491, led July 2'1, 1935 (RCV Docket 4440). l

The output from the oscillator I3, however, is maintained at a constant level so as to produce a correspondingly constant record on the lm or other medium in the recorder I9.

In the reproducer of Fig. 2, which is in this case illustrated as a conventional lm type reproducer, light from the exciter lamp 20 passes through the record strip or nlm F to the photocell 2l. Since there is no requirement for high fidelity in the reproduction of control tracks, a comparatively simple reproducer may be used without the relatively complicated and precise optical system used in playing the sound record, although the latter type of optical system may be used if desired. The output from the photocell 2l passes through the transformer 22 Ato the amplifier tube 23, which is of the variable gain type, such, for example, as an RCA type 6K7. Since all the control frequencies are recorded on the single control track, the effect of all these frequencies will be similarly amplified by theA tube 23.

The tube 23 is provided with the usual bias resistor 24 and bypass condenser 25 and with the usual suppli7 resistor 26 for the screen grid. Plate current is fed to the tube 23 through the resistor 28, and the A. C. output from the plate of the tube 23 passes through' the primary of the transformer 21, and to' ground through the condenser 29. The secondary ofthe transformer 21 is connected as shown to a group of band pass lters 30, 3|, 32 and 33, which separate the several f control frequencies and direct them to the appropriate variable gain amplifiers as described in the aforesaid patents and applications. The several band pass filters 30 to 33 correspond in the frequencies which they pass to the oscillators I tc I3, and the filter 33 accordingly passes the frequency recorded by the oscillator I3 at a constant intensity. It will be apparent that if there is any variation in the-brightness of the exciter lamp 29, sensitivity of the photocell 2 I, or in the density of the lm F, it will produce a corresponding variation in the amplitude of the signals transmitted by the lter 33,

The signals from th'e filter 33 are amplified by the ampliier 34 and fed through the transformer 35 to the rectifier 36, which is preferably a full wave rectifier as illustrated. The rectified output from the tube 36 is iiltered through an appropriate filter circuit consisting of the resistors 38 and 39 and the capacitor 40. The resistor 38 also provides a conductive connection from the ground terminal of th'e bias resistor 24 to the control grid of the tube 23. An appropriate source of voltage 31 is provided to delay the eect of the rectified output from the tube 36 upon the gain of the tube 23.

I'he system is adjusted by varying the gain of the amplier 34 and the amount of the delay voltage 31. It will be obvious that instead of the battery 31, as indicated, a potentiometer shunted across a battery or other source 0f voltage supply may be used.

Where there is any variation in the amplitude of the signals fed tothe amplifier 34, this produces a corresponding variation in the rectiiled output from the tube 36, and this variation in output is transmitted as a variation in grid bias to the control grid of the tube 23. For example, when the output from -the lter 33 decreased, the negative bias on the tube 23 likewise decreases, and there is a corresponding increase in the am- 2,sos,4se

plication produced by the tube 23 tending to restore the signal transmitted b y the lter 33 to its original level.

It will be apparent that by maintaining the signal transmitted by the lter 33 at a constant level by controlling the amplifier 23, the signals transmitted to and by the lters 30 to 32 will be similarly controlled in level and maintained at a level at all times proportional to the level at which they were originally recorded.

It Will be apparent to those skilled in the art that this invention is not limited to its application to controlling control tracks, but that the constant frequency signal may be similarly used to maintain the proper level of reproduction of a sound track directly. For example, a sound input may be substituted for the oscillators I0 to I2 and the oscillator I3 may produce a sub-audible or super-audible signal. In this case, the sound `reproducers would be substituted for the filter y circuits 39 to 32 and the reproduced sound would be maintained at all times in a constant relation to its original recorded level.

Having now described my invention, I claim:

1. The method of recording and reproduction including the recording of at least one signal record which is to be controlled, simultaneously recording a. signal of constant value, reproducing said controlled signal and said constant value signal together, and maintaining the level of said controlled signal solely by said constant value signal.

2. The method of recording and reproduction including the recording of at least one signal record which is t0 be controlled, simultaneously recording a signal of constant value, 'reproducing said controlled signal and said constant value signal together, and maintaining the level of said controlled signal by maintaining said constant value signal at a uniform reproduction level.

3. The method of signal recording including the steps of recording signals of variable value and simultaneously and synchronously recording an independent signal of constant value in the same track with said signals of variable value.

4. 'I'he method of signal recording including the steps of recording signals of variable amplitude and simultaneously and synchronously recording an independent signal of constant amplitude in the same track with said signals of variable amplitude.

5. The method of signal reproduction comprising the steps of simultaneously reproducing a plurality of signals one of which is properly reproducible only at a constant value, separating said constant value signal, and solely utilizing said constant value signal for maintaining the level of all of said signals.

6. The method of signal reproduction comprising the steps of simultaneously reproducing a plurality of signals one of which is properly reproducible only at a constant amplitude, separating said constant amplitude signal, and solely utilizing said constant amplitude signal for maintaining the level of all of said signals.

7. Sound recording apparatus comprising means for recording in a single track a plurality 9. Sound reproducing apparatus including means for picking up a plurality of signals ineluding one continuous signal of constant amplitude, means for amplifying said signals, means for separating said signal of constant amplitude from the remainder of said signals, and means for controlling said amplifying means in accordance with said constant amplitude signal.

10. Sound reproducing apparatus including photoelectric means for reproducing 'a plurality of accordance with said constant amplitude signal.,

11. 'Ihe method of signal recording including the steps of recording signals of variable ampli--v tudey and constant frequency and simultaneously and synchronously recording an independent signal of constant amplitude and constant frequency in the same track with said signals of variable amplitude.

signals of variable amplitude and constant frequency and simultaneously 'and synchronously recording in the same record arca an independent signal of constant amplitude and const-ant frequency.

13. Sound recording apparatus including` means for recording in a single recording area at least one` signal of variable amplitude and constant frequency, and means for recording in the same record area a continuous signal'of constant amplitude and constant frequency,

14. Sound recording apparatus comprising means for recording in a single record area a plurality of signals eachef variable amplitude and constant frequency, and means for recording inthe same record area a signal of constant amplitude and frequency,

HILLEL I.' REISKIND. 

